Barrier coatings are desirable for many applications, such as food packaging and other product packaging. These barrier coatings minimize transmission of oxygen, and water vapor to varying degrees, through the coated substrate. For many end uses, it is desirable for the coating to be clear. When the substrate is also clear, as in a transparent polymer film, view through the substrate is not obstructed. However, known barrier coatings have suffered from numerous limitations, including high cost, inadequate transparency and limited barrier properties. In addition, many barrier coatings used in the past are not capable of being recycled, such as some polyvinyl chloride coatings. There is a need for barrier coatings that address one or more of these problems. A need also exists for barrier coatings that are adapted for application to polymer film substrates. Coatings adapted for in-line application during film manufacture are also desirable.
For instance, barrier coatings for films such as polyester films are disclosed in U.S. Pat. No. 6,709,735 entitled “Oxygen Barrier Coating and Coated Film”, which issued on Mar. 23, 2004 and which is herein incorporated by reference. More particularly, the '735 patent discloses a barrier coating for films that includes an aqueous solution of a copolymer of maleic acid and acrylic acid in combination with polyvinyl alcohol. The inventions disclosed in the '735 patent represent great advances in the art. The present disclosure is directed to further improvements in barrier coatings for films.